Immunoassay devices that make use of immunochromatography are often utilized as a means to test a biological sample for the presence of an analyte of interest, such as a drug of abuse. For example, in many of these immunoassay devices and methods, a specified volume of a biological sample can be contacted with one end of a test strip that contains a colored reagent and that also contains an antigen or antibody dried to the test strip in discrete zones. In this regard, as the biological sample is wicked up by the test strip, the analyte in the sample reacts with the antigens or antibodies and any reactions, if present, can then simply be observed by the appearance or non-appearance of color in the discrete zones.
Given the relative ease with which the immunoassay results can be read, a number of immunoassay devices and methods have been developed to date that allow for the rapid screening of drugs of abuse or other analytes of interest in biological fluids. Many of these prior immunoassay devices and methods, however, have required significant pre-treatment steps where the biological sample must first be modified with specific reagents to dilute or denature any interferents, to modify the analyte structure, and/or to release the analyte from binding molecules prior to adding the biological sample to the testing device. Additionally, in many of these prior devices and methods, once the test sample is introduced, there has been no control provided over either the speed or the timing of the subsequent immunoassay reactions. Indeed, in a number of the prior devices and methods, the quantity of the reaction mixture placed in the testing device is the major factor that determines the speed and timing of all of the subsequent reactions and, in many instances, this ultimately leads to an inefficient or inaccurate result.
Accordingly, a device and method for testing a biological sample for an analyte of interest, such as a drug of abuse, that allows for not only control over the biological sample being tested, but that also allows for the quick and accurate testing of drugs of abuse or other analytes of interest would be both highly-desirable and beneficial.